This invention relates to papermaking and to particulate additives useful therein. Specifically, this invention involves a combination of titanium dioxide and zeolite which provides excellent properties when included in paper.
Paper is essentially a composite of various cellulose fibers with various particulate materials included therein for various reasons. In particular, white materials of low abrasivity are desired. Such materials should improve the optical properties of the paper such as brightness and opacity. Titanium dioxide is a very desirable material, providing outstanding whiteness as well as other optical qualities to various white papers. However titanium dioxide is an expensive material, and finding materials that can complement its contribution in papermaking has been difficult.
Japanese patent application No. Sho 45-41044 with a disclosure date of Dec. 23, 1970, teaches that paper can be made using a natural zeolite as a filler, but only if the material is considerably refined. French Pat. application No. 80 24735 with publication No. 2,494,736 and publication date May 28, 1982, teaches that Zeolite NaA can be used as a partial replacement for TiO.sub.2 in paper. While paper can be made with such systems, there are various problems associated with the process. The chemistry of Zeolite NaA is not conducive to all papermaking methods and may require undesirable additions of other ingredients.
It is an object of this invention to provide an improvement to the process of making paper using zeolite, said improvement being an altered chemistry for Zeolite A and/or carefully controlling the particle size.